Inter-cylinder air-fuel ratio imbalance determination apparatus for internal combustion engine

a technology of air-fuel ratio and determination apparatus, which is applied in the direction of electric control, instruments, braking systems, etc., can solve the problems of difficult to determine whether or not the inter-cylinder air-fuel is due to the imbalance state of the inter-cylinder air-fuel ratio

Active Publication Date: 2013-10-15
TOYOTA JIDOSHA KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0012]In this case, if the threshold value for imbalance determination is set at (to) a value Pith slightly smaller than the imbalance determination parameter P4, an erroneous determination that the inter-cylinder air-fuel ratio imbalance state has occurred is made in the vehicle A under the EGR normal state. If the threshold value for imbalance determination is set at (to) a value P2th slightly smaller than the imbalance determination parameter P3, an erroneous determination that the inter-cylinder air-fuel ratio imbalance state has not occurred is made in the vehicle B under the EGR abnormal state. Accordingly, one of objects of the present invention is to provide an inter-cylinder air-fuel ratio imbalance determination apparatus which can determine that an inter-cylinder air-fuel ratio imbalance state due to the EGR gas (EGR abnormal state) has occurred as accurately as possible.
[0084]This enables to easily obtain the imbalance determination parameter which represents the fluctuation of the air-fuel ratio of the exhaust gas.

Problems solved by technology

That is, an inter-cylinder air-fuel ratio imbalance state due to the EGR gas occurs.
However, it is not easy to determine whether or not the inter-cylinder air-fuel ratio imbalance state due to the EGR gas occurs using the conventional inter-cylinder air-fuel ratio imbalance determination apparatus.

Method used

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  • Inter-cylinder air-fuel ratio imbalance determination apparatus for internal combustion engine
  • Inter-cylinder air-fuel ratio imbalance determination apparatus for internal combustion engine
  • Inter-cylinder air-fuel ratio imbalance determination apparatus for internal combustion engine

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first embodiment

Configuration

[0129]FIG. 5 schematically shows the configuration of a system which is configured in such a manner that a determination apparatus according to a first embodiment (hereinafter also referred to as the “first determination apparatus”) is applied to a spark-ignition multi-cylinder (straight 4-cylinder) four-cycle internal combustion engine 10. Although FIG. 5 shows the cross section of a specific cylinder only, the remaining cylinders have the same configuration.

[0130]The internal combustion engine 10 includes a cylinder block section 20 including a cylinder block, a cylinder block lower-case, an oil pan, etc.; a cylinder head section 30 fixedly provided on the cylinder block section 20; an intake system 40 for supplying gasoline gas mixture to the cylinder block section 20; and an exhaust system 50 for discharging exhaust gas from the cylinder block section 20 to the exterior of the engine 10.

[0131]The cylinder block section 20 includes cylinders 21, pistons 22, connectin...

second embodiment

[0319]Next will be described a determining apparatus (hereinafter simply referred to as a “second determining apparatus”) according to a second embodiment of the present invention. The second determining apparatus is different from the first determining apparatus only in that the second determining apparatus changes an EGR execution region on the basis of whether or not the EGR supplying state imbalance determination parameter Pon has already been obtained and whether or not the EGR stop state imbalance determination parameter Poff has already been obtained, to thereby obtain the both parameters as soon as possible. Accordingly, a description will be made focusing on these differences.

[0320]A CPU 71 of the second determining apparatus sets the EGR execution region as follows.

(Case 1)

[0321]The CPU 71 sets the EGR execution region to a usual EGR execution region, when neither the EGR supplying state imbalance determination parameter Pon nor the EGR stop state imbalance determination p...

third embodiment

[0343]Next will be described a determining apparatus (hereinafter simply referred to as a “third determining apparatus”) according to a third embodiment of the present invention. The third determining apparatus is different from the second determining apparatus only in that:

[0344]the third determining apparatus allows the imbalance determination parameters (the EGR supplying state imbalance determination parameter Pon and the EGR stop state imbalance determination parameter Poff) to be obtained when the engine rotational speed NE and the load of the engine 10 is in a predetermined parameter obtaining region;

[0345]the third determining apparatus sets the narrowed EGR execution region to a region which is within the usual EGR execution region but is outside of the parameter obtaining region; and

[0346]the third determining apparatus sets the expanded / enlarged EGR execution region to a region which is obtained by adding a “region, which is within the parameter obtaining region, but with...

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Abstract

An inter-cylinder air-fuel ratio imbalance determination apparatus (determination apparatus) according to the present invention obtains, as an “EGR supplying state imbalance determination parameter”, a value corresponding to a differential value d(abyfs)dt of a detected air-fuel ratio abyfs represented by an output value of an air-fuel ratio sensor when an EGR gas is being supplied, and obtains, as an “EGR stop state imbalance determination parameter”, a value corresponding to a differential value d(abyfs)dt when an EGR gas supply is being stopped. The determination apparatus obtains an “EGR-causing imbalance determination parameter Pegr” by subtracting the EGR stop state imbalance determination parameter Poff from the EGR supplying state imbalance determination parameter Pon, and determines that an inter-cylinder air-fuel ratio imbalance state has occurred due to the supply of the EGR gas when the parameter Pegr is larger than a threshold Pegrth.

Description

TECHNICAL FIELD[0001]The present invention relates to an “inter-cylinder air-fuel ratio imbalance determination apparatus for an internal combustion engine”, which is applied to a multi-cylinder internal combustion engine having an EGR gas supply means, and which can determine (monitor / detect) that a degree of imbalance among the air-fuel ratios of air-fuel mixtures, each supplied to each of cylinders (inter-cylinder air-fuel ratio imbalance; inter-cylinder air-fuel-ratio variation; or inter-cylinder air-fuel-ratio non-uniformity) has increased excessively.BACKGROUND ART[0002]A widely adapted electronic-fuel-injection-type internal combustion engine has at least one fuel injection valve (fuel injector) at each of the cylinders or at each of intake ports communicating with each of the cylinders. Accordingly, when the characteristic / property of the fuel injection valve of a certain specific cylinder changes to inject fuel in an amount excessively larger than an instructed fuel injecti...

Claims

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Application Information

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Patent Type & AuthorityPatents(United States)
IPC IPC(8): B60T7/12
CPCF02D41/0065F02D41/0085F02D41/1454Y02T10/47Y02T10/40
InventorMIYAMOTO, HIROSHIIWAZAKI, YASUSHISAWADA, HIROSHI
OwnerTOYOTA JIDOSHA KK